With champion Dominick Cruz still sidelined due to a knee injury, the interim beltholder Barao will defend against the highly regarded up-and-comer McDonald.

Barao, 25, a Brazilian jiu-jitsu black belt, is undefeated since dropping a decision in his April 2005 professional debut.

After successive submissions of Anthony Leone and Chris Cariaso under the WEC banner, Barao rattled off wins over Cole Escovedo, Brad Pickett and Scott Jorgensen to earn his interim title shot.

Barao turned in a career-defining effort at UFC 149 last July, outclassing former WEC featherweight champion Urijah Faber over five one-sided rounds.

A training partner of current 145-pound king Jose Aldo at Nova Uniao, Barao possesses many similar traits as he systematically breaks opponents down with his muay thai base, while always threatening with an elite grappling game.

Following a more dominant performance against Faber than we saw from the champ Cruz, Barao made a case for himself being the man to beat at 135 pounds.

McDonald, 22, a BJJ brown belt, is undefeated in four UFC appearances. The Oakdale MMA product is coming off back-to-back knockout wins over Alex Soto and Miguel Torres.

The explosive California native has great timing, which will be a critical tool against the fast-charging Brazilian.

McDonald epitomizes the new breed of the sport, having trained in all disciplines since debuting in November 2007.

The young challenger has all the traits of a future champion, but Barao presents a stiff step up in competition. Barao's speed and power shots will play a major factor as he avoids McDonald's counters and makes him pay.

We've already witnessed the knockout power of both men, so this bantamweight barnburner could end at any moment. At such a high level, however, we should anticipate five competitive rounds with Barao's output and counters being the deciding factors.

Verdict: Barao via decision

-Dustin Poirier (13-2) vs. Cub Swanson (18-5)

In a critical featherweight contest, the 24-year-old Poirier and 29-year-old Swanson hope to cement their place in the top 10 of the division.

Poirier, a BJJ brown belt, rebounded from a losing effort in a 2012 "Fight of the Year" candidate against Chan Sung Jung by finishing Jonathan Brookins this past December.

In previous appearances, the American Top Team member defeated Josh Grispi, Jason Young, Pablo Garza and Max Holloway.

The Louisiana native is a savvy submission player with a constantly improving striking base. But he could find himself in a heap of trouble if he engages Swanson in a brawl.

Swanson, a longtime representative of Jackson's MMA in New Mexico, experienced a career resurgence in 2012, recording second-round stoppages of George Roop, Ross Pearson and Charles Oliveira.

The Californian has yet to erase the memory of a punishing eight-second knockout loss to Jose Aldo at WEC 41 in June 2009 and he's hoping to make the case for a rematch with another strong finish.

Swanson has established himself as one of the best sluggers at featherweight. Despite Swanson's ability to hold his own on the ground, his best work is done when he's swinging heavy leather in close quarters.

The momentum may be swaying in Swanson's favor, but Poirier will be looking to expose him where he's most vulnerable. Poirier will seize his opportunity to secure a takedown and lock in a submission, coaxing a tapout midway through the fray.

Verdict: Poirier via Submission, Round 2

-Cyrille Diabate (19-8-1) vs. Jimi Manuwa (12-0)

In a fan friendly 205-pound pairing, the French kickboxer Diabate will look to hand the undefeated Nigerian prospect Manuwa his first professional loss.

Diabate, 39, has a wealth of experience competing all over the globe. The highly technical southpaw is riding a pair of wins over Tom DeBlass and Chad Griggs. However, Diabate's limited grappling abilities have hindered his consistency over the years.

Manuwa, 32, finished Kyle Kingsbury in his promotional debut this past September. Still perfect in 12 professional appearances, the London-based striker is a powerhouse who isn't afraid to trade loaded artillery.

In a matchup of talented kickboxers, Diabate should have the edge. The Frenchman's technical expertise will be the difference maker as he targets the legs and body of his opponent before breaking him down late.

Verdict: Diabate via TKO, Round 3

-Gunnar Nelson (10-0-1) vs. Jorge Santiago (25-10)

In a welterweight tilt, the 24-year-old submission ace Nelson will look to keep his perfect record intact against the returning 32-year-old veteran Santiago.

Nelson wasted little time putting his submission prowess on display, finishing DaMarques Johnson in the first round of his UFC debut this past September.

A BJJ black belt under Renzo Gracie, the Iceland native is a two-time Pan American gold medalist and former NAGA grappling world champion.

Santiago makes his Octagon return after a pair of first-round finishes of Leoanrdo Pecanha and Justin Guthrie under the Titan Fighting Championship banner.

The Rio de Janeiro native now trains with the Blackzilians in Florida, where he made the cut to 170 pounds in an attempt to rejuvenate his career.

A former Sengoku and Strikeforce middleweight champion, Santiago struggled in his last go-around with the promotion, dropping a pair of middleweight bouts to Brian Stann and Demian Maia.

A BJJ black belt himself, Santiago has never been finished by submission, which makes this a particularly intriguing fight.

Santiago should have an edge with his striking and his experience will also be beneficial. But Nelson's grappling game is on another level. Finishing Santiago could prove difficult, but Nelson should dominate the positional game en route to a triumphant decision.

Verdict: Nelson via Decision

-Ryan Jimmo (17-1) vs. James Te Huna (15-5)

In an international tussle of 31-year-old light heavyweight prospects, the Canadian Jimmo battles the New Zealander Te Huna.

Entering the UFC with a reputation for winning forgettable decisions, Jimmo made a prolific statement when he finished Anthony Perosh in just seven seconds, tying the record for the fastest knockout in UFC history.

The former Maximum Fighting Championship titleholder has spent time training with Florida's Blackzilians camp as he continues to round out his game, which relies heavily on wrestling.

Te Huna is riding a three-fight winning streak. Most recently, Te Huna earned "Fight of the Night" honors for his decision over Joey Beltran last July.

The Australian-based scrapper is an aggressive power puncher with great strength, which doesn't bode well for Jimmo in his sophomore UFC outing.

Te Huna should easily stuff Jimmo's takedown attempts, while landing the heaviest shots standing. After three rounds of relentless pressure, Te Huna should be rewarded on judges' scorecards.

Verdict: Te Huna via Decision

-Che Mills (15-5) vs. Matthew Riddle (7-3)

Welterweights will kick off the main card as Britain's own Mills takes on the Pennsylvania native Riddle.

Mills, a former Cage Rage British welterweight champion, was stopped by red-hot contender Rory MacDonald at UFC 145 before bouncing back with a first-round finish of Duane Ludwig in September.

A vicious muay thai striker, there are really no secrets when it comes to Mills' strategy.

Riddle, a BJJ purple belt, may need to rely on superior submission skills to come out on top. Riddle is unbeaten in his last three fights, including a unanimous decision over John Maguire in November.

Armed with a wrestling base, the Throwdown Training Center product is slowly evolving as a striker. We're finally seeing him use his reach advantage, but he still lacks the power to threaten sturdy chins.

With no fear of being knocked out, Mills will come forward aggressively and test Riddle's defense early. He'll need to be weary of the takedown, but it should only be a matter of time until Mills flattens his American adversary to mark a successful homecoming.

Verdict: Mills via KO, Round 2

Preliminary Card (Facebook):

-Terry Etim (15-4) vs. Renee Forte (7-2)

The 27-year-old British banger Etim and 25-year-old "TUF: Brazil" cast member Forte will clash in lightweight action.

Etim is a dynamic kickboxer with a potent submission game. He makes his long awaited return after being on the losing end of the 2012 "Knockout of the Year" against Edson Barboza at UFC 142.

Consistency has been Etim's worst enemy, but the Liverpool native is an extremely talented prospect who has yet to achieve his full potential.

Forte was submitted in his first post-reality show appearance, succumbing to a third-round rear-naked choke against Sergio Moraes in October.

The Team Nogueira product will be making a much needed cut to 155 pounds, but Etim should have him covered in all areas. Etim will tee off on the Brazilian with a cavalcade of strikes before finishing him off with a combination.

Verdict: Etim via TKO, Round 2

-Danny Castillo (14-5) vs. Paul Sass (13-1)

A pair of quality lightweight prospects on the rebound trail are set to cross paths as the 33-year-old Californian Castillo meets the 24-year-old Liverpool native Sass.

Castillo's three-fight winning streak was snapped this past October as the Team Alpha Male product was knocked out by Michael Johnson.

Sass, also a BJJ brown belt, saw his perfect run come to an end this past September as the sublime grappler lost at his own game, succumbing to a first-round armbar against Matt Wiman.

With 12 submission wins in 14 professional fights, Sass has excelled against less seasoned grapplers. Evidenced in his loss to Wiman, the step up in competition will result in hiccups.

Castillo's submission defense is excellent, but his willingness to tangle with superior grapplers has cost him in the past. If Castillo opts to keep the fight standing, he should be successful. However, Castillo's wrestling instincts will eventually kick in. If he engages Sass on the mat, the British submission magician will have the last laugh.

Verdict: Sass via Submission, Round 2

-Josh Grispi (14-4) vs. Andy Ogle (8-2)

The 24-year-old Grispi and 23-year-old Ogle meet in a must-win featherweight bout.

Grispi desperately needs to rebound from a career-worst three-fight losing streak against Dustin Poirier, George Roop and Rani Yahya.

Once thought to be the No. 1 contender to Jose Aldo's throne, the Massachusetts native now finds himself fighting for his place on the roster.

Ogle suffered a split decision loss in his UFC debut against Akira Corassani in September. The Newcastle native will need to feed off the home crowd against a more seasoned combatant.

The step down in competition should allow Grispi to rekindle some of the success he experienced during his WEC run that saw him defeat Mark Hominick, Micah Miller, Jens Pulver and L.C. Davis.

Grispi's superior striking will be apparent from the get-go as he gets the best of key combinations and transitions, coming away with the nod after 15 minutes.

Verdict: Grispi via Decision

-Stanislav Nedkov (12-0) vs. Tom Watson (15-5)

In a middleweight melee, the 31-year-old Bulgarian standout Nedkov competes at 185 pounds for the first time against the 30-year-old Southampton native Watson.

Still technically perfect as a professional, Nedkov was finished by Thiago Silva in a light heavyweight bout this past November, but the result has since been overturned to a no-contest after Silva tested positive for marijuana metabolites.

At 205 pounds, the BJJ black belt Nedkov recorded some impressive victories over the likes of Travis Wiuff and Luiz Cane.

Watson, who splits time training with Tristar Gym and Jackson's MMA, dropped a split decision to Brad Tavares in his UFC debut this past September.

The former BAMMA and UCMMA middleweight champion is a household name in the U.K., so he should have the frenzied fans solidly rooting him on.

Watson is a proficient kickboxer, but Nedkov's power will be the difference maker. Nedkov already overwhelmed most foes at 205 pounds, so he should be a menace at middleweight.

Nedkov will land heavy shots to set up takedowns. Watson could certainly take a punch, but judges will likely side with Nedkov if it goes the distance.

Verdict: Nedkov via Decision

-Vaughan Lee (12-8-1) vs. Motonobu Tezuka (19-5-4)

In a bantamweight bout, Birmingham's 30-year-old Lee takes on the 25-year-old Japanese prospect Tezuka.

Lee last saw action in July, suffering a first-round submission loss to T.J. Dillashaw. In his prior appearance, Lee submitted one-time pound-for-pound great Norifumi "Kid" Yamamoto on his home soil at UFC 144 in Japan.

The Ultimate Training Centre product is primarily a submission practitioner, but the southpaw continues to develop into a well-rounded fighter.

Tezuka came up short in his UFC debut this past November, dropping a split decision to Alex Caceres. The longtime Pancrase and DEEP veteran is a judo and zendokai karate black belt, in addition to a BJJ brown belt. Although Tezuka's credentials may be impressive, his grappling-based offense could play right into the hands of Lee.

The home crowd and stylistic advantages tend to fall into Lee's lap, so he should eke out the nod after three rounds.

Verdict: Lee via Decision

-Ulysses Gomez (9-3) vs. Phil Harris (21-10)

Flyweights will kick off the festivities in London as the 29-year-old California native Gomez takes on the 29-year-old Brit Harris.

The inaugural Tachi Palace Fights flyweight champion Gomez was knocked out in the first round of his promotional debut against John Moraga this past August.

The BJJ black belt has submitted seven of his nine career victims, a testament to his ground game.

A native of Portsmouth, Harris was submitted in his October UFC debut against Darren Uyenoyama.

Harris is also primarily a grappler with 13 submissions in 21 career victories.

Harris may have more professional bouts under his belt, but Gomez has benefited from fighting a higher caliber of competition.

Gomez should land the crisper combinations before finishing off the British hopeful by submission.